Clot resistant multiple lumen catheter

ABSTRACT

Blood is circulated through a multiple lumen catheter which connects between a vein of a patient and the blood treatment device. The catheter and the lumens thereof each define distal ends which are positioned within the vein. By this invention, one withdraws blood from the vein through one of the lumens at a flow rate of at least about 200 ml./min. while also inserting blood into the vein through another of said lumens at a similar flow rate. The distal ends of the lumens are longitudinally spaced from each other by no more than about 5 mm. It has been found that the following advantages can be achieved by this method: less clot formation coupled with low direct blood recirculation and longer catheter survival. Also, the catheter of this invention works well in either direction of blood flow through the respective lumens.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 08/891,766, filed Jul.14, 1997, which is a division of application Ser. No. 474,376, filedJun. 7, 1995, now U.S. Pat. No. 5,685,867, which is a division ofapplication Ser. No. 08/386,473, filed Feb. 9, 1995, now U.S. Pat. No.5,569,182.

BACKGROUND OF THE INVENTION

Multiple lumen catheters are in clinical use as blood access devices foreasy and safe connection to hemodialyzers, or other blood treatmentdevices. Their use is desirable for chronic medical conditions, wherefrequent treatment of the blood of a patient is required, requiringfrequent access to the vascular system.

Such catheters have a distal end which is implanted typically in a veinof the patient, while the proximal end of the catheter, when in use,communicates with a tubular set or the like which permits thecirculation of blood from the vein, through the catheter, and throughthe set to a blood processing device such as a hemodialyzer. Then, theblood moves through typically another tubular set back to another lumenof the catheter, and then back to the vein of the patient.

Jugular and subclavian multiple lumen catheters are typically intendedas permanent blood access devices. Femoral catheters are typically usedas an intermediate-term blood access devices, which are expected to beremoved after a period of time.

In the clinically used double lumen catheters for hemodialysis, thelumen for outflow of blood back into the vein terminates approximately20-30 mm. beyond the lumen for inflow, which draws in blood. The purposeof this is to prevent direct recirculation of blood, which is when bloodreturned by one catheter lumen flows directly into the other catheterlumen again. This, of course, reduces the efficiency of the bloodtreatment process. This is the case for the catheters which areclinically used, and also are illustrated in Mahurkar U.S. Pat. No.4,895,561; Martin U.S. Pat. No. 5,156,592; and Twardowski et al. U.S.Pat. No. 5,209,723.

Other multiple lumen catheters have flush ends in which the distal endsof the lumens terminate at the same longitudinal position along thecatheter, such as in Sisley et al. U.S. Pat. No. 4,405,313. However,these catheters are not used for the withdrawing and reintroducing oflarge amounts of blood of a patient as is done in hemodialysis. Rather,such catheters are for the infusion of medications and/or parenteralnutrition, with only the occasional withdrawal of a sample of blood.Thus, the issue of direct blood recirculation is not a problem, andthere distal end thus is designed without regard to solution of theblood recirculation problem.

The catheters for hemodialysis require high blood flows of typically 200ml per/min or more for efficient dialysis. The direct recirculation ofblood as defined above causes a reduction in the effective blood flowand thus decreases the efficiency of dialysis. Essentially, each percentof blood recirculation that is present in a catheter decreases theeffective blood flow by the same one percent, which, of course, reducesthe efficiency of dialysis.

In multiple lumen catheters, direct blood recirculation values of lessthan 15 percent are generally deemed acceptable. To achieve this, in theprior art it was believed to be mandatory to longitudinally space thedistal ends of the inlet catheter lumen and the outlet catheter lumen byabout 20-30 millimeters in order to avoid unduly high directrecirculation. However, several disadvantages have been noted by suchlarge longitudinal spacings between the distal ends of the respectivelumens. For example, it may be desired to reverse the blood flow throughthe lumens because the usual inflow lumen is not delivering sufficientblood flow due to clotting. The only other alternative is to remove thecatheter. In this circumstance, the widely spaced lumen ends do not workwell in that and recirculation values rise to undesirable levels. Also,it has been found that blood clots can and do attach immediately distalto the inflow lumen when there is a wide longitudinal spacing betweenthe two distal ends of the catheter lumens.

DESCRIPTION OF THE INVENTION

By this invention, a method is provided of circulating blood through amultiple lumen catheter which connects between the vein of a patient anda blood treatment device. The lumens of the catheter each define distalends positioned within the vein.

In accordance with this invention, one withdraws blood from the veinthrough one of the lumens at a flow rate of at least about 200 ml/min,while inserting blood into the vein through another of said lumens at asimilar flow rate, while the distal ends of the lumens arelongitudinally spaced from each other by no more than about 5millimeters.

The blood flow rate is preferably at least about 300 ml/min. Preferably,the distal ends of the lumens are position ed beside each other withoutlongitudinal spacing, although one lumen, preferably the outflow lumen,may extend beyond the inflow lumen by a distance of no more than about 5mm.

In another embodiment, the lumens may be separated by a wall whichprojects distally beyond the lumen distal ends. This wall may comprisean extension of a septum that extends through the catheter and separatesthe lumens along the catheter length.

Likewise, the distal lumen ends may cause the circulating blood to passthrough the ends in opposite directions, which directions diverge inacute angle relation from each other.

In the prior art, double lumen catheters that are used for hemodialysishave one lumen that projects distally by about 20-30 millimeters fartherthan the other lumen. The farther projecting lumen is typically theblood outflow lumen, while the other lumen is typically the blood inflowlumen, For the purposes below, "poorly functioning catheters" aredefined to be multiple lumen catheters implanted in the patient havingmaterially reduced flow due to obstruction caused by clotting."Well-functioning catheters" are defined to be catheters that areimplanted in a patient and have the expected blood flow characteristicsbecause they are substantially free from clotting.

Recirculation studies show direct recirculation values close to zerowith standard multilumen dialysis catheters having 20-30 mm lumen endspacing (inflow lumen used for inflow and the outflow lumen used foroutflow) and zero to 13 percent with reversed flow (outflow lumen usedfor inflow and the inflow lumen used for outflow), of poorly functionalcatheters. (1.Moss A H, McLaughlin M M, Lempert K D, Holley J L: Use ofthe Silicone Catheter with a Dacron Cuff for Dialysis Short-TermVascular Access. AM J Kidney Dis 1988; 12:492-498. 2.Moss A H, VasilakisC, Holley J L, Foulks C J, Pillai K, McDowell D E: Use of a SiliconeDual-lumen Catheter with a Dacron cuff as a Long-term Vascular Accessfor Hemodialysis Patients. Am. J. Kidney Dis. 1990; 16:211-215).

Our own study (Twardowski ZJ, Van Stone JC, Jones M E, Klusmeyer M SHaynie J D: Blood Recirculation in Intravenous Catheters forHemodialysis. JASN 1993; 3:1978-1981) shows that the directrecirculation values of well-functioning conventional catheters asbefore, with standard lumen flow directions, were close to zero at 300ml/min blood flow and similar to those already reported. Recirculationvalues of poorly functional catheters with reversed flows through thelumens were higher than those with standard lumen flow but not exceeding15%. However, recirculation values with reversed flow andwell-functioning catheters were much higher (up to 40%), exceeding thosewith reversed flow, poorly functioning catheters.

This represents a significant inefficiency of blood transport which willresult in inefficient dialysis. We speculated that the poorly functionalcatheters contain a clot at the inflow lumen. These clots blocked theoutlet of blood to the catheter, and caused its dispersion and mixingwith the blood flowing back into the vein. The survival probability ofpoorly functioning catheters is markedly reduced, but they may functionseveral months, and are frequently used until they completely fail.

Well-functioning catheters do not contain any obstacle to the outflowingblood stream with reversed lumens. Laminar flow of this blood streamalong the catheter wall is believed to cause its free passage by theinflow lumen, thus allowing its suction into the inflow blood lumen.

This study prompted us to propose that the distance between inflow andoutflow tubing might be markedly shortened to 5 mm or less without arisk of undue recirculation. We further propose that the shortening ofthe outflow tubing beyond the inflow lumen end can decrease the clotretention on the outflow tubing, and thus improve the function of thecatheter. An experience with fourteen such catheters confirmed ourpredictions, and showed that the flow problems with such catheters aresignificantly less. As predicted, direct recirculation values at 300ml/min with double lumen catheters that have distal lumen endslongitudinally spaced by about 5 mm., using the standard flow direction,were close to zero (Mean±SD) (1.59%±4.35%). Moreover, the recirculationvalues at 300 ml/min with reversed flow in such well-functioning, doublelumen catheters turned out to be less than the values for catheterswhere the distance between lumens was 20-30 mm (Mean±SD) (4.17%±7.34%).

Further, catheters with flush inflow and outflow lumen boresside-by-side tend to not exhibit high direct recirculation at higherblood flows.

We made prototypes of such catheters with flush inflow and outflow lumenbores (zero longitudinal spacing of the distal lumen ends). The catheterwas implanted through the right internal jugular vein into the rightatrium. Arbitrarily one blood flow direction was called "standard", andthe opposite direction was called "reversed." Measurements of directrecirculation in three such catheters shows the following directrecirculation values in percent:

    ______________________________________    Flow   Flow            Standard                                  Flow        Standard    (ml/min)           direction                    Mean   Deviation                                  direction                                         Mean Deviation    ______________________________________    100    Standard 21.5   2.4    Reversed                                         14.8 1.6    300    Standard 9.3    1.4    Reversed                                         6.5  1.4    500    Standard 8.7    1.9    Reversed                                         10.7 1.8    ______________________________________

Direct recirculation at low blood flow (100 ml/min) can be seen to behigher than the same at high blood flows (300 and 500 ml/min).Apparently, at low flow rate, the velocity of the stream is insufficientto prevent outflowing blood from being sucked into the inflow lumen.Thus, normal flow direct recirculation values of catheters having flushlumen ends are similar to catheters having lumen ends spaced by 20-30 mmwith standard flows at high blood flows. However, the directrecirculation values of the reversed flow catheters of this inventionare lower than similar reversed flow catheters with 20-30 mm spacing ofbetween inflow and outflow lumen distal ends. The catheter of thisinvention thus provides sufficient blood flow with acceptable lowrecirculation in either flow direction, contrary to those of the priorart,

There are two major advantages with the catheter of this invention:

1. The recirculation is similar in either direction of the blood flow.

2. The probability of blood clot attachment at or immediately distal tothe inflow lumen is less likely because there is little or no supportfor such an attachment. Consequently, such a catheter will provide goodflow, fewer clotting problems, and longer survival.

In this invention, the typical catheters for long-term hemodialysisaccess are intended to be inserted into the superior vena cava or rightatrium through one of the following veins:

1. Right internal jugular vein

2. Left internal jugular vein

3. Right subclavian vein

4. Left subclavian vein

For intermediate-term blood access, the catheter may be inserted intothe common iliac vein or inferior vena cava through a femoral vein. Theoverall design of the catheters may be similar to those in U.S. Pat. No.5,209,723, except as otherwise disclosed herein.

In one embodiment of the invention, the catheter inflow and outflowbores are flush, but separated by a small septum typically extendingabout 1-5 mm beyond the lumen bores. Such a septum decreases bloodrecirculation. In these embodiments, the direction of blood flow throughthe catheter lumens does not strongly affect blood recirculation. Also,a small-sized septum is unfavorable for the firm anchoring of the clot.Small clots attached to the septum may be washed away by alternatingflow directions with consecutive dialyses. The lumen bores may beslightly angled at their distal ends.

In yet another embodiment of the invention, the catheter outflow boreextends beyond the inflow bore by no more than 1-5 mm. Such aconfiguration provides recirculation values close to zero with standardflow, and minimal (less than those with conventional tip configuration)recirculation with reversed flow. Such a small-sized outflow lumenextension is unfavorable for the firm anchoring of clots.

DESCRIPTION OF THE DRAWINGS

In the drawings, FIG. 1 is a perspective view of a double lumen dialysiscatheter, shown to be implanted intravenous system of a patient;

FIG. 2 is an enlarged, plan view of one embodiment of the distal tip ofthe catheter in accordance with this invention;

FIG. 2a is a perspective view of the distal tip of FIG. 2a;

FIG. 3 is a perspective view of the distal tip of a modified catheter ofFIG. 2;

FIG. 4 is an enlarged, plan view of the distal tip of another embodimentof catheter in accordance with this invention;

FIGS. 5 and 6 are perspective views of different embodiments of catheterdistal tips similar to that of FIG. 4;

FIG. 7 is an enlarged, plan view of another embodiment of the distal tipof the catheter of this invention;

FIG. 8 is a perspective view of the distal tip shown in FIG. 7;

FIG. 9 is a perspective view of another embodiment of catheter as shownin FIG. 7;

FIG. 10 is an enlarged, plan view of another embodiment of catheterdistal tip in accordance with this invention;

FIG. 11 is a perspective view of the catheter distal tip of FIG. 10; and

FIG. 12 is another embodiment of catheter distal tip of the type shownin FIG. 10.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to FIG. 1, a catheter 10 in accordance with this invention isshown implanted in the right atrium 11 of the heart through the rightjugular vein of a patient. The implantation is intended to be permanent,with the result that the patient can be freed from the burden of needle"sticks" three times a week or so with a pair of fistula needles.Rather, the catheter 10 can be simply connected and disconnected todialysis sets through a Y-connector 12, each branch of whichcommunicates with one of lumens 14, 16, which are shown in FIGS. 2-12,for example.

The overall design of catheter 10 may be conventional, and may be of anyof the embodiments described in the Zbylut J. Twardowski et al. U.S.Pat. No. 5,405,320. Also, catheter 10 may be implanted in otherpositions of the body, as desired.

Catheter 10 is shown to be implanted in its natural, unstressed shape,which corresponds in the distal section of the catheter with the shapeof the vein or veins in which catheter 10 resides. Such cathetersexhibit less pressure and abrasion against the blood vessel walls,resulting in a reduction in blood clotting and tissue irritation.

Catheter 10 also has a pair of conventional tissue adhering cuffs, 17,18, for permanent implantation of the catheter in the patient as isshown. The distal end of catheter 10, carrying Y site 12, then projectsoutwardly from an incision site 19 through the skin.

The distal end of catheter 10 extends, as previously stated, into theright atrium 11 of the heart, although such positioning is merelypreferable and not essential to the invention.

The remaining FIGS. 2-12 pertain to differing designs of catheter,particularly with reference to the design of the catheter distal end 13.Any of the designs disclosed may be used with any type of catheter ofany desired overall shape, particularly those previously described inthe patents cited above and the prior cited Twardowski et al. U.S. Pat.No. 5,405,320.

FIGS. 2 and 2a show a tip 13 of catheter 10 which comprises a basicallyflat catheter end 19 which, if desired, may be slightly convex if notflat. Catheter 10 is a double lumen catheter having lumens 14, 16 andmay be in generally oval cross-section is shown in FIG. 2a. Therespective lumens, 14, 16 are separated by a septum 21 that extendssubstantially the entire length of the catheter, so that lumen 14 cancommunicate with tubular branch 23 of the Y-connector, and tubular 16can connect with the tubular branch 25, for separate flow communication.Lumens 14, 16 each typically have a diameter of at least 2 mm.

Thus, blood can flow from a set connected to one of the branches ofY-connector 12, preferably at a flow rate of at least about 200 ml/min.Blood is then simultaneously withdrawn through the other lumen of thecatheter and passes through the other tubular branch of the Y-connector12, so that a constant stream of blood may be provided to a dialysissystem or the like and then returned to the patient.

It is believed that because of the relatively high velocity of theblood, little direct recirculation of blood flow is encountered betweenthe blood pouring into the atrium 12 from lumen 14 and the blood whichis being taken up again through lumen 16.

Referring to FIG. 3, a modified embodiment 13a of the catheter tip isshown, with the remainder of the catheter being typically of similardesign. As before, a pair of lumens 22, 24 are provided in a mannersimilar to lumens 14, 16 in the preceding embodiment. The tip of thiscatheter is flat in its cross-section, similar to the previousembodiment.

Referring to FIG. 4, another embodiment 13b of catheter tip is shownhaving double lumens 30, 32, which end flush with each other as shown.However, in this embodiment, septum 34 extends about 1-5 mm (typically 3mm) beyond the ends of lumens 30, 32. Such a short septum 34 providesimprovements in the reduction of immediate blood recirculation from onelumen to the other, while at the same time, the septum extension 34 istoo short to support a significant amount of blood clotting. It can beseen that septum 34 comprises an extension of the internal septum 21bfound in this and most double lumen catheters.

FIG. 5 shows a perspective view of one embodiment of the catheter tip ofFIG. 4. Lumens 30a, 32a are separated by a septum 34a which has acylindrical recess 35 on each side thereof to facilitate blood inflowand outflow from the lumens 30a, 32a.

Referring to FIG. 6, another perspective view of a catheter distal endis shown, being another possible embodiment of the catheter tip of FIG.4. The catheter tip in this embodiment is round in cross-section withlumens 30b, 32b assuming a D-shaped cross-section and a greater height.Also, septum 34b is of the shape of a flat plate, without the recessesof the previous embodiment. Septum 34b also extends about 1-5 mm beyondthe lumen bores, for example, 4 mm, and represents an extension of theinternal septum that extends the length of the catheters disclosedherein.

Referring to FIG. 7, a catheter tip 13c is shown, comprising the twolumens 48, 50, similar to previous embodiments, with lumens 48, 50 beingseparated by septum 55 in a manner also similar to the previousembodiments. In this embodiment, the distal tip face comprises lumenends which, in cross-section, comprise flat faces 52, 54 which are in anobtuse angle relation to each other, preferably an angle to each otherof 100-170° so that each face is angled at about 10-45° to a planeperpendicular to the longitudinal axis of the catheter.

Referring to FIG. 8, one embodiment of FIG. 7 is shown in which lumens48a, 50a terminate in angled relationship as shown.

Referring to FIG. 9, a catheter of different cross-sectional shape isshown, resulting in different cross-sectional shapes for lumens 48b, 50band their end faces 52b, 54b.

It can be seen that, in the catheters of the previous embodiments, it issubstantially immaterial which of the lumens is the inflow lumen andwhich of the lumens is the outflow lumen since the catheters aresymmetrical. Referring, however, to FIG. 10, asymmetrical catheterdesigns are shown which can provide advantageous blood flowcharacteristics with low direct blood recirculation and low long-termclotting at the catheter distal tips.

FIG. 10 shows a catheter tip 13d which has a pair of lumens 56, 58separated by a septum 60, in which the distal end of 64 of lumen 58extends about 1-5 mm beyond the distal end 66 of lumen 56, for example,5 mm. In this embodiment it is generally advantageous for lumen 58 to bethe blood outflow lumen, while lumen 56 is the blood inflow lumen,taking blood into the catheter for conveyance and processing in adialyzer for the like. However, good results are achieved with reverseflow at 200 ml./min. or more.

As shown in FIG. 11, the extension 65 of lumen 58a beyond the end 67 oflumen 56a may define a side groove 69. which is basically a cylindricalsection, to facilitate blood flow either into or out of lumen 56a. Inthis embodiment, lumens 56a, 58a are seen to be round in cross-section.

However, in FIG. 12, a similar overall structure is shown as anotherembodiment of FIG. 10, in which the lumens 56b, 58b and their respectiveends 64b, 66b are in the same relationship as shown in FIGS. 10 and 11,but due to the cross-sectional dimensions of the catheter, the lumensare D-shaped, as shown.

Here, it is generally preferred for the outflow lumen to be lumen 58,58a, or 58b while the inflow lumen is lumen 56, 56a, or 56b. Because thelumen ends 65, 70 extend no more than about 5 mm beyond the ends 66, 67,71 of lumens 56, 56a, 56b, the catheters of this design have reduced,clinically disadvantageous direct blood recirculation. The above designsalso suppress clot formation at the catheter distal tip.

The above has been offered for illustrative purposes only, and is notintended to limit the scope of the invention of this application, whichis as defined in the claims below.

That which is claimed:
 1. A multiple lumen catheter for thebidirectional, continuous transport of blood, said catheter comprisingat least a pair of lumens having open, distal ends, said distal endsbeing longitudinally spaced from each other by no more than about 5 mm.,said lumens each having substantially identical diameters of at leastabout 2 mm., to permit blood flow through each lumen at a flow rate ofat least about 200 ml./min.
 2. The catheter claim 1 in which said lumendistal ends are positioned beside each other without longitudinalspacing.
 3. A multiple lumen catheter for the bidirectional, continuoustransport of blood, said catheter comprising at least a pair of lumenshaving open, distal ends, said distal ends being positionedsubstantially beside each other without longitudinal spacing, saidlumens being of a size to permit a blood flow rate simultaneouslythrough both lumens of substantially at least 200 ml./min. in eachlumen, said catheter carrying at least one fibrous tissue attachmentsite.
 4. The catheter of claim 3 in which said catheter defines aproximal section for implantation with an end portion of said catheterprojecting proximally out of the skin of said patient, said proximalsection carrying a pair of fibrous implantation sites in spaced relationto each other.